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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jesper Dangaard Brouer <brouer@redhat.com>,
        Pavel Popa <pashinho1990@gmail.com>,
        David Ahern <dsahern@gmail.com>,
        Jason Wang <jasowang@redhat.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.19 021/139] virtio-net: disable guest csum during XDP set
Date:   Tue,  4 Dec 2018 11:48:22 +0100
Message-Id: <20181204103650.849650686@linuxfoundation.org>
In-Reply-To: <20181204103649.950154335@linuxfoundation.org>
References: <20181204103649.950154335@linuxfoundation.org>
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4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Wang <jasowang@redhat.com>

[ Upstream commit e59ff2c49ae16e1d179de679aca81405829aee6c ]

We don't disable VIRTIO_NET_F_GUEST_CSUM if XDP was set. This means we
can receive partial csumed packets with metadata kept in the
vnet_hdr. This may have several side effects:

- It could be overridden by header adjustment, thus is might be not
  correct after XDP processing.
- There's no way to pass such metadata information through
  XDP_REDIRECT to another driver.
- XDP does not support checksum offload right now.

So simply disable guest csum if possible in this the case of XDP.

Fixes: 3f93522ffab2d ("virtio-net: switch off offloads on demand if possible on XDP set")
Reported-by: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Pavel Popa <pashinho1990@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/virtio_net.c |    8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -70,7 +70,8 @@ static const unsigned long guest_offload
 	VIRTIO_NET_F_GUEST_TSO4,
 	VIRTIO_NET_F_GUEST_TSO6,
 	VIRTIO_NET_F_GUEST_ECN,
-	VIRTIO_NET_F_GUEST_UFO
+	VIRTIO_NET_F_GUEST_UFO,
+	VIRTIO_NET_F_GUEST_CSUM
 };
 
 struct virtnet_stat_desc {
@@ -2285,9 +2286,6 @@ static int virtnet_clear_guest_offloads(
 	if (!vi->guest_offloads)
 		return 0;
 
-	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
-		offloads = 1ULL << VIRTIO_NET_F_GUEST_CSUM;
-
 	return virtnet_set_guest_offloads(vi, offloads);
 }
 
@@ -2297,8 +2295,6 @@ static int virtnet_restore_guest_offload
 
 	if (!vi->guest_offloads)
 		return 0;
-	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))
-		offloads |= 1ULL << VIRTIO_NET_F_GUEST_CSUM;
 
 	return virtnet_set_guest_offloads(vi, offloads);
 }